The invention relates to a method of transferring between switching centers the handling of an active connection between a user, on the one hand, and a mobile terminal, on the other hand, in a telecommunication system designed for mobile communication, comprising at least one mobile terminal, a first and a second switching center designed for mobile services and each having a working region with a limited range, and a communication network designed for nonmobile telecommunication, which network has switching centers, hereinafter referred to as "exchange" centers able to interact with the switching centers designed for mobile services, there being a first route between the first switching center and the user, via which first route the active connection has been set up, and there being a second route between the second switching center designed for mobile service and the user, which routes each have at least one intelligence point where connection control and call control can be handled separately from each other, a capability which is a definition of the term "intelligence point" as used hereinafter.
Such a method is disclosed by EP 0 421 535 A1 and allowed U.S. patent application, Ser. No. 07/900,521. The latter describes how an existing method for transferring between two switching centers designed for mobile services the active connection to a mobile terminal, better known under the designation "handover procedure" and as defined, for example, in GSM recommendations for the future pan-European digital mobile telecommunication system, can be improved. In addition to a number of attractive aspects, this existing method has the great drawback that the switching center via which the active connection is initiated remains incorporated in the communication path to the mobile terminal for the entire duration of the connection, even if said connection moves to the working region of another switching center. Another drawback of this existing method is that the first switching center involved in an active connection provides the billing for the entire time that the connection is active, as a result of which it is not possible to adjust the billing if the mobile station moves to a region having a different charge rate. The method described in EP 0 421 535 A1 does not have the above drawbacks because, in this method, in addition to a connection set up between the exchange center designed for nonmobile telecommunication and the first switching center, a connection is set up between the first and the second switching exchange center and between the center designed for nonmobile telecommunication and the second switching center, and the entire handling of the connection is taken over by the second switching center, after which the connection between the two switching centers and between the exchange center designed for nonmobile telecommunication and the first switching center is disconnected. As a result, the switching center via which the active connection is initiated is not incorporated in the communication path to the mobile terminal for the entire duration of the connection and it is possible to adjust the billing.
This known method described in EP 0 421 535 A1 has the disadvantage that the setting up of the connection between the second switching exchange center and the center designed for nonmobile telecommunication to which the first switching center is already connected may result in inefficient routing depending on the way in which the user may be coupled to one or both switching exchange centers via various centers designed for nonmobile telecommunication or via a third switching center and depending on the facilities of said exchange centers designed for nonmobile telecommunication and on the switching centers. Some switching centers, for example, have the possibility of being able to handle connection control and call control separately, as a result of which it becomes possible to reroute an existing connection without having to interrupt or disconnect it for a long time. As defined, for example, in GSM recommendations, at least one such switching center is always present in every route between the mobile terminal and the user.